Electrical resistance element and method of producing same



SR I XR 1 93729652 l 0m STATES "yss REFERENCE PATENT OFFICE.

JOHN G. CLEMENS, OI! BUFFALO, NEW YORK.

No Drawing. 5

possess the characteristic of lowering in resistance as .its temperature is increased so as to prevent a heavy surge of current when starting the motor. 7

Another object of the invention is to provide a resistance element possessing the characteristic above mentioned, which element will ossess a constant initial resistance and W111 therefore resume its degree of initial resistance 4 after current has been passed through it in efi'ecting starting of the motor and the resistance is'subsequently cut out of circuit and allowed to cool.

The invention also has as one of its objects to evolve a novel method whereby a resistance element possessing the characteristic above mentioned may be economically and readily produced.

I In its simplest form the resistance element is produced in the following manner:

A suitab e quantity of reduced iron or what is known as iron-by-hydrogen is mixed with water to the consistency of a paste and this paste is then introduced into a suitable mold form where it is molded substantially to cylindrical form. The unit thus produced is then removed from the mold and dried by heat, and after it has been sufiiciently dried, it is brought to a red heat and is finally permitted to cool. If the resistance element in this form is subjected, for example, to a flow of current of ten volts at-twenty amperes, the current will gradually rise from zero to twenty amperes but I have found that after the current has been cut oil and the resistance element has been permitted to cool and the circuit is again closed through the said element, the rise of amperage will begin somewhat above zero, tor example at ten amperes, indicating that the initial flow of- Specification of Letters Patent. Patented luar. 22, 1921. Application filed May 7, 1919. Serial No. 295,263.

current through the resistance element has somewhat decreased its resistance. I have found, however, that by a further step in the method of manufacture, this decrease in resistance may be effectually overcome. This step consists in initially passing through the resistance element a heavy current as for ex ample a current of ten volts rising to one hundred amperes or more. The resistance element thus acted upon by this final step, I have found, will subsequently invariably transmit current with the rise of ampera e beginning approximately at zero so that m its completed form the element will possess a constant initial degree of resistance.

The resistance element prepared as above set forth is especially adapted for heavy duty work but where such. an element is to be employed in connection with lighter work, there is mixed with the reduced iron a quantity of nonconducting substance proportionate to the increased resistance which it is desired to obtain. For this pur pose I. may employ high resistance carborundum, sand, or in fact any non-conducting substance miscible with the reduced iron and water paste.

The resistance elements may, of course, be molded in any desired sizes and in use an assemblage 0 any desired number of the elements may be employed. In the use of the resistance element the same is interposed in the motor circuit and the circuit is so controlled as for example by a double throw switch, that it may first be closed through the resistance element whereupon the element will rise in temperature'and as the ;temperature increases will offer less and less resistance until the desired amount of current is passing to the motor whereupon the switch 1s thrown So as to directly connect the motor to the supply line.

It will be understood, of course, that in drying out the molded but unfinished resistance element, the water will be driven off and due to the finely reduced state of the iron-by-hydrogen, the dried article will be somewhat of a porous nature; that is to say it will not be as compact as though it were molded from poured molten iron nor will it possess the grain of molded iron. However, in the step of heating the element to dull red heat, union between the minute particles of the mass is brought about to such an extent that without losing its porous SEARCH ROOM nature, the element will be apparently of solid and compact nature. The porosity of the element is no doubt one of the controlling factors which so well adapts the element to perform the functions of a resistance and in the novel manner heretofore pointed out and while I prefer to employ iron-by-hydrogen, it will be understood, of course, that I might find it advisable to make use of iron reduced by some other method than that which is followed in producing iron-by-hydrogen, and might even find it desirable to employ some other metal in a finely divided state if suitable as an electric resistance.

It will also be understood that if I find it desirable, I may manufacture and placeupon the market the resistance elements without the final step of treatment which comprises the passing of a heavy current of high amperage with, of course, the'conseuent loss of the advantages to be gained by t is step in the method.

Having thus described the invention, what is claimed as new is 1. The method of producing an electrical resistance element which comprises molding the element from a paste of a finely divided resistance metal, heating. the element to a temperature to drive off the moisture, and

subsequently heating the element to a dull red heat.

2. The method of producing an electrical, resistance element which comprises molding the element from a mass of finely divided resistance metal and passing a heavy current through the element.

' 3. The method of producing an electrical resistance element which comprises molding the element from a mass of finely divided resistance metal and passing a heavy current at gradually increasing amperage through the element.

- 4. The method of producing an electrical resistance element which comprises molding the element from a paste of a finely divided resistance metal, eliminating moisture from the element, heating the element to a dull red heat, and when cool passing a heavy current therethrough.

5. The method ofproducing an electrical resistance element which comprises molding the element from a paste of a finely divided resistance metal, eliminating moisture from the element, heating the element to a dull red heat, and when cool passing a' heavy current at a gradually increasing amperage therethrough.

In testimon whereof I aflix .m signature.

J O G. CLEMEN [1 s.] 

